Oxime, such as cyclohexanone-oxime, diacetylmonoxime and acetoxime, is an important chemical intermediate that is used as an important raw material for synthesis of organosilicon crosslinking agent, as boiler deoxidizer and as anti-skinning agent for painting and coating. It plays a key role in industrial application.
The traditional method for oxime production is hydroxylamine method, which is time-consuming and complicated. It needs to use strong acid having rigorous corrosion resistance requirement for equipment, and likely resulting in many environmental problems. This method is being phased out gradually. The successful development of titanium silicalite molecular sieve (TS-1) initiated an environmental-friendly chemical process based on the zeolite catalyst. The one-step synthesis of oxime product can be realized with ketone ammoximation reaction catalyzed by the TS-1 in the presence of hydrogen peroxide. The method has attracted extensive attention with mild conditions and high reaction efficiency. However, a large volume of solvent like tert-butyl alcohol is added in the ammoximation reaction, and such solvent needs to be recycled in the subsequent process. Consequently, the industrial energy consumption increases, and the use of solvent aggravates the environmental pollution. Therefore, the development of solvent-free ammoximation process has significance on application. The ammoximation reaction is a heterogeneous catalytic process in which mass transfer is greatly affected by solvent. As a result, the key point of solvent-free ammoximation reaction is to realize the effective mass transfer for solution-to-solution and solution-to-catalyst.
Some domestic studies on the solvent-free oxime production method have been carried out: invention patent CN 103288678A and invention patent CN 103288679A use water as the solvent to carry out cyclohexanone ammoximation reaction, but the conversion rate of cyclohexanone is as low as about 40.0%; invention patent CN 103288677A adopts TS-1/CNF composite catalyst and water (solvent) to carry out cyclohexanone ammoximation reaction, which requires expensive composite catalyst and a large amount of water increasing the energy consumption of subsequent oxime-water separation; and invention patent CN 101318912A carries out butanone ammoximation reaction without organic solvent, but the diacetylmonoxime yield is only 70.3%.